1. Field of the Invention
The present invention relates to an ink supply for an ink-jet printer and, more particularly, to a replaceable ink supply having a self-contained pump that can be actuated to supply ink from a reservoir within the ink supply to the print head of an ink-jet printer.
2. Description of Related Art
Ink-jet printers have become established as reliable and efficient printing devices. Typically, an ink-jet printer, utilizes a print head mounted on a carriage which is moved relative to a printing surface. A control system activates ink jets on the moving print head at the appropriate locations causing the print head to eject, or jet, ink drops onto the printing surface to form desired images and characters.
To work properly, such printers must have a reliable supply of ink for the print head. Many ink-jet printers use a disposable ink pen that can be mounted to the carriage. Such an ink pen typically includes a print head and a reservoir for containing an ink supply for the print head. The ink pen also typically includes pressure regulating mechanisms to maintain the ink supply at an appropriate pressure for use by the print head. When the ink supply is exhausted, the entire ink pen is replaced. This system provides an easy, user friendly way of providing an ink supply for an inkjet printer.
An important characteristic of a printer is the speed with which it can print. In ink-jet printers, one way to increase this speed is to move the print head more quickly. However, in a printer using an ink pen, the entire ink pen, including the reservoir, is moved with the print head. This makes it desirable to keep the reservoir as small as possible so that the ink pen has less mass, allowing it to be moved more quickly and efficiently. On the other hand, a smaller reservoir will be exhausted more quickly and, hence, requires more frequent replacement and disposal of the ink pen.
The problems posed by size limitations of the ink reservoir have been heightened by the increasing popularity of color printers. In a color printer, it is usually necessary to supply more than one color of ink to the print head. Commonly, three or four different ink colors, each of which must be contained in a separate reservoir, are required. The combined volume of all of these reservoirs is limited in the same manner as the single reservoir of a typical one-color printer. Thus, each reservoir can be only a fraction of the size of a typical reservoir for a one-color printer.
Furthermore, when even one of the reservoirs is depleted, the ink pen may no longer be able to print as intended. Thus, the ink pen must typically be replaced and discarded when the first of the reservoirs is exhausted. This further decreases the useful life of the ink pen.
As can be appreciated, the print head and pressure regulating mechanisms of the ink pen contribute substantially to the cost of the ink pen. These mechanisms can also have a useful life expectancy far longer than the supply of ink in the reservoir. Thus, when the ink pen is discarded, the print head and pressure regulating mechanisms may have a great deal of usable life remaining. In addition, in multiple color ink pens, it is unlikely that all of the ink reservoirs will be depleted at the same time. Thus, the discarded ink pen will likely contain unused ink as well as a fully functional print head and pressure regulating mechanism. This results in increased cost to the user and a somewhat wasteful and inefficient use of resources.
To alleviate some of the problems associated with disposable ink pens, some ink-jet printers have used ink supplies that are not mounted to the carriage. Such ink supplies, because they are stationary within the printer, are not subject to all of the size limitations of an ink supply that is moved with the carriage. Some printers with stationary ink supplies have a refillable ink reservoir built into the printer. Ink is supplied from the reservoir to the print head through a tube which trails from the print head. Alternatively, the print head can include a small ink reservoir that is periodically replenished by moving the print head to a filling station at the stationary, built-in reservoir. In either alternative, ink may be supplied from the reservoir to the print head by either a pump within the printer or by gravity flow.
However, such built-in reservoirs are frequently difficult and messy to refill. In addition, because they are never replaced, built-in ink reservoirs tend to collect particles and contaminants that can adversely affect printer performance.
In view of these problems, some printers use replaceable reservoirs. These reservoirs, like the built-in reservoirs are not located on the carriage and, thus, are not moved with the print head during printing. Replaceable reservoirs are often plastic bags filled with ink. The bag is provided with a mechanism, such as a septum which can be punctured by a hollow needle, for coupling it to the printer so that ink may flow from the bag to the print head. Often, the bag is squeezed, or pressurized in some other manner, to cause the ink to flow from the reservoir. Should the bag burst or leak while under pressure, the consequences can be catastrophic for the printer.